Plastiglomerate: 'Rocks' made up of plastic waste and coral rubble identified in Indonesia

After similar cases in Trindade (Brazil) and Hawaii, a new form of "plastiglomerate" rock has been identified. Image: Birgit Mohr / Kiel University

Scientists recently identified a very specific form of pollution in plastic fragments that become embedded in the rocks of the coastlines in some parts of the world. This is known as "plasticrust." Recently, a team of researchers has identified a similar phenomenon in Indonesia, only this time, it involves rock-like compounds made up of plastic waste and coral rubble.

After similar cases in Trindade (Brazil) and Hawaii, a new form of "plastiglomerate" rock has been identified. A plastiglomerate is a "rock" made of a mixture of beach sediment or other natural debris (like shells or wood) and plastic. These compounds echo the "plasticrust" discovered in Madeira in 2016 by Portuguese scientists, a form of pollution caused by plastic debris becoming embedded in coastal rocks. However, the recent discovery in Indonesia involves new, rock-like compounds made from plastic waste and coral rubble, which is debris from loose or dead coral skeletons.

According to the German-Indonesian team behind this discovery, this new type of plastiglomerate "rock" comes from the burning of plastic waste on beaches covered with these coral fragments. And the problem could be significant, since the melted plastic these "rocks" contain is contaminated with organic pollutants, the researchers report in a news release. To reach this conclusion, the authors analyzed 25 samples taken from the beaches of Panjang Island, located to the west of the Indonesian island of Java. These were then analyzed in a laboratory by researchers at Kiel University, Germany.

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"Until now, there have been rather basic studies describing the formation of plastiglomerates. With our results, we have shown for the first time how plastiglomerate differs from other plastic waste and can make better statements about its environmental impact," says first author Dr Amanda Utami, who works as a scientist at Indonesia's largest science organization (BRIN, Badan Riset dan Inovasi Nasional).

Published in the journal, Scientific Reports, the results of this research describe how when plastic waste is burnt directly on the beach, the melting and combustion process produces plastiglomerate "rock." This phenomenon is potentially all the more harmful because this chemically degraded plastic decomposes more rapidly into microplastics under the action of the wind and the waves. These are then released into the environment and could potentially find their way into the food chain.

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"These new types of plastic pollution could be an important vector for chemical contamination of nearby coastal habitats such as coral reefs, seagrass meadows, and mangroves," the scientists warn. "If trash from urban areas on tropical beaches were better disposed of and managed, a serious problem could be prevented," Dr Amanda Utami concludes.